Shannon participated in a national math contest by taking a math test. The test results followed a normal distribution with a mean score of 72.6 points out of 100 and a standard deviation of 8.7. Shannon received a score of 81 points. Shannon thinks she performed better than 68% of the students in the contest
Shannon is incorrect because her score of 81 is...
a. approximately −2 standard deviations from the mean
b. approximately −1 standard deviations from the mean
c. approximately 1 standard deviations from the mean
d. approximately 2 standard deviations from the mean